Glade 2 Tutorial
Renartthefox writes "Rikke D. Giles has written a new tutorial for Glade II. Glade is a program designed to enable the quick building of graphical user interfaces for GTK+ and GNOME applications. However, it can be used with any desktop environment in linux, as long as the GTK+ and/or GNOME libraries are installed."
XUL may be slow but it is more portable than GTK+ is.
Yes I know there is a GTK+ port for Windows but neither it is fast itself or just having Windows support in addition to X11 support is enough.